RCT of a Brief Motivational Intervention for College Student Marijuana Use

Introduction: Marijuana is the most frequently reported illicit substance used on college campuses; however few published intervention studies have focused specifically on addressing high-risk marijuana use in this college or university setting. Marijuana use is associated with both short-and long-term consequences, including poor academic performance and attendance, impaired cognitive functioning, deficits related to attention and memory, respiratory problems, and increased heart rate, among others. There is a growing body of research suggesting motivational enhancement interventions may be efficacious for reducing substance use in the context of selective and indicated prevention and treatment.  The present study evaluated the efficacy of an in-person brief motivational enhancement intervention for reducing marijuana use and related consequences among frequently using college students.

Method: Participants included 212 college students from two campuses who reported frequent marijuana use (i.e., using marijuana at least 5 times in the past month) who were recruited from a random sample from University registrars’ lists. Participants completed web-based screening and baseline assessments and, upon completion of the baseline survey, were randomized to either receive an in-person brief intervention or to an assessment-only control group. Follow-up assessments were completed approximately three and six months post-baseline. Marijuana use was measured by number of days used in the last 30 days, typical number of joints used in a typical week in the last 60 days, and marijuana-related consequences.

Results:  Results indicated significant intervention effects on number of joints smoked in a typical week and a trend toward fewer marijuana-related consequences compared to the control group at three-month follow-up. Specifically, intervention participants reported 24% fewer joints smoked per week relative to control participants (RR = .76, 95% CI [0.60 - 0.96]) at three months, but groups did not differ at six months. Similarly, there was a trend for intervention participants reporting 10% fewer marijuana problems relative to control participants at three months (RR = 0.90, 95% CI [0.76 – 1.07]), which was also not statistically significant at six months. Reported 30 day use was similar across groups at both three and six months, after controlling for baseline use.

Conclusion: This study provides preliminary data on short-term effects of an in-person focused brief marijuana intervention for college students at reducing marijuana use during the academic quarter. While more research is needed, we would tentatively endorse this approach for campuses considering options for responding to students who violate substance use policies related to marijuana.